Wind turbines are located in wind corridors, on mountains and near mountain passes where higher surface winds exist. Windmills/turbines operate below 1,000 feet above ground level (agl) and are subject to surface wind restrictions. Because of this loss in wind speed, windmill farms design for taller and taller turbine blades. Presently, megawatt (MW) wind turbine blades may reach in excess of 500 feet above ground level. Both large MW and small kilowatt (KW) wind turbines are typically designed for air speeds from 15 miles per hour (mph) to 30+ mph, and create little or no energy when winds are below 10 mph.
For wind power to have a broader rural use and application the windmill needs to produce large quantities of energy while utilizing average local wind conditions. In one exemplary locality (McKinney, Tex.) over a two-year period (2011-2012), the highest wind speed was about 13 mph, the lowest wind speed was about 6 mph, and the overall average wind speed was 9 mph. However, the overall average wind speed of 9 mph is exceeded for only 5 months out of the year. In such an exemplary locality, for the windmill to be effective throughout the year; the windmill needs to operate with winds as low as 6 mph.
A simple construction and ease of maintenance gives the windmill a broader appeal.
A windmill design is heretofore needed that can effectively and efficiently operate in 9 mph or less, surface wind conditions. The vertical axis windmill of the following disclosure accomplishes the above and other objectives, and overcomes at least the above-described disadvantages of conventional windmills.